The Echimyidae family is the largest group of Hystricognathi rodents, with 28 genera and 103 species, which are widespread throughout South and Central America. Despite a remarkable degree of karyotypic diversity, with a diploid number (2n) ranging from 14 to 118 and autosomal fundamental number (FNa) ranging from 14 to 168, the karyotypes of eight genera are not known. Here, we determine the karyotype of Echimys chrysurus species from the eastern Amazon, based on two samples collected in Paragominas and Santa Bárbara municipalities, Pará state, Brazil. The karyotype was analysed through G-banding, C-banding, and Fluorescence In Situ Hybridization (FISH) with telomeric and 18S rDNA probes. Echimys chrysurus has a 2n=80/FNa=134 karyotype. The autosomal set consists of 28 meta/submetacentric pairs (1-28) and 11 acrocentric pairs (29-39); the X chromosome is large and acrocentric, and the Y chromosome is small and acrocentric. The constitutive heterochromatin is distributed in small amounts at the centromeric region of all autosomes and the X- and Y-chromosomes. FISH with telomeric probes showed only distal signals, and FISH with rDNA 18S probes exhibited a signal in the interstitial region of a small metacentric pair. Echimys chrysurus is nested within a cluster with 13 other Echimyini (Echimyinae) representatives, in which about 89% of the karyotypes show a tendency towards high 2n (50-118) and an elevated number of biarmed chromosomes (FNa=100-68). Similar to the other three subfamilies, the Echimyinae have karyotypes exhibiting high and low 2n (from 14 to 118) but with distinct 2n ranges: Capromyinae (34-88), Carterodontinae (66), and Euryzygomatomyinae (32-65). The majority of Echimyidae taxa exhibit distinct karyotypes for each species but with a prevalence of biarmed chromosomes, regardless of the 2n value. This indicates that the chromosomal evolution of this family was complex and with intense genomic reshuffling due to several rearrangements, such as fusion/fission, pericentric inversions, and multiple translocations.